How to fix a 3D scanned object with texture in Blender?
If you want a clean mesh out of your 3D scan you should first 

Do a retopology of your 3D scan. Basicly treat it as if it were sculpted.
https://www.youtube.com/watch?v=k9NAv_q_wfU

If you plan of doing this more often think about buying Blender Retopo Tools: https://www.youtube.com/watch?v=0ZH8RJDr6pg

Here is a quick and dirty retopo guide for 3d scans:
https://www.youtube.com/watch?v=LbtWoJXbytM

Lastly transfer UV coordinates from your 3D scan to the new (retopo) mesh.
Can I transfer an already made UV to another object?